Ventajas
From an IT perspective, (a common TeleTech phrase) TeleTech is a fast paced, under powered, and over committed company. As such, it provides a great environment for highly self-motivated and ambitious individuals who are early in their career looking to learn as much as possible as quickly as possible. There are a variety of technologies employed so you can increase both your depth and breadth of knowledge in core technology products. It's also a favorable environment for those who "work well under stress." If you can survive TeleTech, you can thrive anywhere.
Desventajas
There is no concept of a work/life balance. Everybody in IT is on call for some level of escelation 24/7. Personally, I spent many stretches of months where I worked 70+ hours per week. If you have a spouse or children, this becomes an increasingly important issue while management typically cared increasingly less. It was not uncommon to see co-workers in their offices crying because of the high amount of stress. The joys and pains of working at TeleTech depend very much on your immediate manager. I've had managers who worked very hard with upper management to bring about changes while most managers I've had rolled over and did what was easiest for themselves. Aside from that, there seemed to a lay off program at least once per year. And, in some instances, people who did not see eye to eye with their manager (not performance issues) would be terminated under the guise of these lay offs. This, in turn, made more work for those who were left since the position could not legally be filled for some time.